Here's the background:
Western Maryland, 31" frost line, this will be a 20x20 shop attached
to the back of my attached unheated garage. The floor will be about 1
foot above grade at the highest point, sloping to channel water away
from the house.
I've been told of two main options, perimeter foundation (either
poured concrete or 8" concrete blocks) with a pier in the middle
supporting engineered floor joists, or a poured foundation, lined with
1" rigid insulation boards laid vertical around the perimeter, filled
with rubble, 1" rigid insulation boards laid horizontal next to the
vertical insulation, with a concrete pad poured over that.
This latter appeals to me because it is supposed to keep the concrete
floor from being so cold in the winter (cold would have to travel past
the vertical insulation and past the horizontal insulation to cool the
pad)(I'm heating the shop with a safe propane heater) and there is no
crawl space, vented or otherwise, to mess around with. The crawlspace
would be inaccessible (not 18" clearance between dirt and joists).
Don't want termites, although there's 8-12 inches from any dirt to
wood, so that may not be a problem.
Shop will be for woodworking (tablesaw, bandsaw, etc.), no plumbing,
one story. I'm perfectly willing to either use rubber mats where I'm
standing or later come in and run 1x over 6mil sheeting, covered by
tongue and groove flooring, but later, much later,hopefully.
Am I missing anything? Is one just dramatically cheaper than the
Thanks for any advice.